1. Field of the Invention
The present invention relates to a control valve in a lubricant supply apparatus for an engine, in particular in a lubricant supply apparatus including a valve gear supply channel through which a lubricant is fed to a cam journal in a cylinder head, and a crank shaft supply channel through which a lubricant is fed to a crank shaft, a connecting rod, and the like in a cylinder block, the control valve adjusting a hydraulic pressure supplied to each of the channels.
2. Description of the Related Art
Attempts have been made to vary the hydraulic pressure of oil fed from an oil pump according to the rotation speed of an engine so as to supply oil with the optimum hydraulic pressure for each rotation speed region. Attempts have also been made to reduce a load on the oil pump by adjusting a hydraulic pressure supplied to each of a valve gear lubrication circuit and a crank shaft lubrication circuit to a value needed for the circuit.
To achieve such an object, an invention disclosed in Japanese Patent Application Laid-Open No. 2009-264241 has been provided. The invention in Japanese Patent Application Laid-Open No. 2009-264241 will be described below in brief. Reference numerals in the following description are the same as reference numerals described in Japanese Patent Application Laid-Open No. 2009-264241. First, oil is pumped from an oil pan 10 by an oil pump 12 and fed to a first feeding path 16a and a second feeding path 16b. 
The first feeding path 16a is a path that supplies oil mostly to a bearing portion 18 of the crank shaft. The second feeding path 16b is a path that supplies oil to, for example, a valve gear mechanism 20. A hydraulic control valve 22 is disposed on the first feeding path 16a to control the amount of oil supplied to the bearing portion 18 of the crank shaft. The hydraulic control valve 22 is configured such that an output hydraulic pressure from the hydraulic control valve 22 is controlled by a control unit 24.
The control unit 24 is controlled by an engine rotation speed sensor 26, an engine load sensor 28, an oil temperature sensor 30, and a hydraulic pressure sensor 32. A relief valve 34 is provided to transfer an excessive hydraulic pressure to the oil pan 10 through an oil path portion between the oil pump 12 and a filter 14 when the hydraulic pressure exceeds a predetermined value. In the above-described configuration, the hydraulic control valve 22 is controlled by the control unit 24.
The invention in Japanese Patent Application Laid-Open No. 2009-264241 and conventional techniques including similar configurations have the following problems. The invention in Japanese Patent Application Laid-Open No. 2009-264241 utilizes electronic control as control means. To allow the hydraulic control valve 22 to be controlled utilizing electronic control, much information on the rotation speed of the engine, an oil temperature, an engine load, the hydraulic pressure, and the like needs to be acquired. Furthermore, complicated control such as MAP control and oil temperature compensation is needed. This may significantly increase costs. Moreover, driving the hydraulic control valve 22 leads to power consumption, and a power generator needs to be driven, possibly increasing the engine load.
Additionally, if an electric system for any of the various sensors, the hydraulic control valve 22, the control unit 24, and the like becomes defective, the control is prevented from being sufficiently performed, thus precluding expected effects from being produced. Thus, an object of the present invention (technical problem to be solved) is to provide an inexpensive and reliable control valve by using a hydraulic driving mechanism to avoid the inherent problem of electronic control.